This invention relates to portable stretchers, and more particularly, to a stretcher which can be collapsed into a compact, easily carried, size.
Litters, or stretchers, for field use must be strong and durable for carrying injured persons over rough terrain for long distances. However, when not in such use, these stretchers must be foldable to a compact, easily transportable package, as a back pack, for example. Until now, collapsible stretchers have been cumbersome and somewhat difficult to move about. There is a pressing need in the military and medical field for an all-purpose stretcher which is light, quickly assembled and disassembled, compact in the collapsed state and therefore easy to handle by soldiers and medics.
Many prior art stretchers have frame poles with joints so that the stretcher can be folded. To our knowledge, no prior art stretchers are capable of being folded to such a compact size that it can be easily carried, on the back, for instance, and yet still be sufficiently rigid to bear weight when it is in use.
In such stretchers, the joint for a member which folds in the opposite direction of weight-bearing is a particular problem. The lack of a reliable joint of this type has impeded the use of stretchers which can be folded in both directions into a compact package.
Examples of attempts to solve this problem are shown in U.S. Pat. Nos. 3,555,578 - Pile, and 2,650,373 - Zeller, et al. Pile's frame poles have two hinges 11 separated by a support 10, two inner members 12 which fold in the direction of load-bearing and two outer members 14 which fold in the direction opposite to weight-bearing. When the Pile stretcher is extended, cables support the joints against collapsing in the weight-bearing direction. Cables stretch and do not provide the rigidity required in a stretcher. In addition, the central cable support member 10 in Pile prevents folding of the stretcher to a compact size. In Zeller, et al the middle sections 13, 14 and end section 15-16 all fold in the direction of weight bearing. The members 18, 19, and 20 span the folding sections of the pole frames and prevent folding them to a compact size.
It is an object of the present invention to provide a stretcher which folds to a compact size and which can be extended easily into a rigid, load-supporting flat bed surface.
It is another object of the invention to provide a stretcher in which the locking mechanism for the joint is easily actuated when the stretcher is folded or unfolded.